This invention relates to a new method of preparing crystalline aluminosilicate molecular sieve compositions.
Zeolitic materials, both natural and synthetic, are known to have catalytic capabilities for many hydrocarbon processes. Zeolitic materials typically are ordered porous crystalline aluminosilicates having a definite structure with large and small cavities interconnected by channels. The cavities and channels throughout the crystalline material generally are uniform in size allowing selective separation of hydrocarbons. Consequently, these materials in many instances are known in the art as "molecular sieves" and are used, in addition to selective adsorptive processes, for certain catalytic properties. The catalytic properties of these materials are affected to some extent by the size of the molecules which selectively penetrate the crystal structure, presumably to contact active catalytic sites within the ordered structure of these materials.
Generally, the term "molecular sieve" includes a wide variety of both natural and synthetic positive-ion-containing crystalline zeolite materials. They generally are characterized as crystalline aluminosilicates which comprise networks of tetrahedra of SiO.sub.4 and AlO.sub.4 moieties in which silicon and aluminum atoms are cross-linked by sharing of oxygen atoms. The electrovalence of the aluminum atom is balanced by the use of positive ions, for example, alkali-metal or alkaline-earth-metal cations, ammonium ions, or hydrogen ions.
Prior art developments have resulted in the formations of many synthetic zeolitic crystalline materials. Crystalline aluminosilicates are the most prevalent and, as described in the patent literature and in the published journals, are designated by letters or other convenient symbols. Examples of these materials are Zeolite A (U.S. Pat. No. 2,882,243), Zeolite X (U.S. Pat. No. 2,882,244), Zeolite Y (U.S. Pat. No. 3,130,007), Zeolite ZSM-4 (U.S. Pat. No. 3,578,723), Zeolite ZSM-5 (U.S. Pat. No. 3,702,886), Zeolite ZSM-11 (U.S. Pat. No. 3,709,979), Zeolite ZSM-12 (U.S. Pat. No. 3,832,449), and others.
The present invention is a new method of preparing crystalline aluminosilicate molecular sieve compositions using oxygen-containing organic compounds as templates in which the silica/alumina (SiO.sub.2 /Al.sub.2 O.sub.3) ratio can be adjusted to effect better selectivity in hydrocarbon conversion reactions. The crystalline forms, as determined from X-ray diffraction analysis, of these compositions include mordenite-like and ferrierite-like forms and forms exhibited in aluminosilicates identified as ZSM-4 and ZSM-5.
Molecular sieves characterized as "mordenite" by chemical composition and X-ray spectra are known as naturally occurring materials and as synthesized materials. For example, a conventional mordenite sieve is produced by crystallizing a basic mixture of sodium aluminate and an oxide of silicon without the use of an organic template compound. Such mordenites are described in D. W. Breck "Zeolite Molecular Sieves," John Wiley & Sons, 1974, incorporated by reference herein. U.S. Pat. No. 4,061,717 discloses a method of producing a mordenite molecular sieve using an ionene polymer as an organic template compound in the crystallization of the sieve. U.S. Pat. No. 4,107,195 discloses synthetic mordenite prepared as a by-product using 1,4-butanediamine, ethylenediamine and pyrrolidine as organic templates.
Molecular sieves characterized as "ferrierite" by chemical composition and X-ray spectra are known as naturally occurring materials and as synthesized materials. For example, a conventional ferrierite sieve is produced by crystallizing a basic mixture of sodium aluminate and an oxide of silicon without the use of an organic template compound. Such mordenites are described in D. W. Breck "Zeolite Molecular Sieves," John Wiley & Sons, 1974, incorporated by reference herein. U.S. Pat. No. 4,000,248 discloses a method of producing a ferrierite molecular sieve using N-methyl pyridinium hydroxide as an organic template compound in the crystallization of the sieve. U.S. Pat. Nos. 4,016,245, 4,107,195 and 4,046,859 disclose the formation of a ferrierite-like material using an organic template derived from ethylenediamine, pyrrolidine or butanediamine, or organometallic 2-(hydroxyalkyl)trialkylaluminum compounds.
Aluminosilicate molecular sieves identified as ZSM-5 are described in U.S. Pat. Nos. 3,702,886 and 4,139,600. Such aluminosilicates are prepared using organic templates such as tetralkyl ammonium salts, primary alkyl amines and alkylene diamines as described in U.S. Pat. Nos. 4,139,600 and 4,151,189. Aluminosilicate molecular sieve identified as ZSM-4 is described in U.S. Pat. Nos. 3,578,723 and 4,021,447 using organic templates including tetraalkyl ammonium salts, pyrrolidine and choline salts.